Display device and electronic device

ABSTRACT

To mitigate a bending stress in the flexible wiring substrate in a structure, a display panel, to which the flexible wiring substrate connects, is curved along a first direction, and the flexible wiring is bent back to the rear of the display panel. The flexible wiring substrate connects with the display panel at a first region and at a second region; the flexible wiring substrate connects with the wiring substrate at a third region and at a fourth region. The flexible wiring substrate has a narrowest width in the first direction at an intermediate region between the display panel and the wiring substrate. A first wiring group in the flexible wiring substrate connects the first region with the third region or the fourth region, a second wiring group in the flexible wiring substrate connects the second region with another one of the third region or the fourth region.

The present application is a continuation application of InternationalApplication No. PCT/JP2019/050835, filed on Dec. 25, 2019, which claimspriority to Japanese Patent Application No. 2019-000514, filed on Jan.7, 2019. The contents of these applications are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION (1) Field of the Invention

The present invention relates to display devices especially to thedisplay devices in which the substrates can be used in bent state.

The present invention further relates to several electronic devicesincluding display devices, sensors and so forth, in which the flexiblewiring substrates are used.

(2) Description of the Related Art

Self-luminous type display devices like the organic EL display device,the micro-LED display device and so forth, and other display deviceslike the liquid crystal display device and so forth are sometimesrequired to be used in curved state because of their applications andtheir design needs. In addition, not only display devices but also touchpanels or sensor substrates, e.g. photo sensors, are also sometimesrequired to be used in curved state according a design of equipment inwhich those devices are installed. Curving directions in the displaydevices and the sensor substrates are defined along the lateraldirection (may be referred to as x axis direction herein after) or alongthe longitudinal direction (may be referred to as y axis directionherein after).

The flexible wiring substrates are used to supply the power and signalsto the display devices and the sensor substrates; the flexible wiringsubstrates are used in a bent state to avoid the outer sizes of thedisplay devices and the sensor substrates become too large. Patentdocuments 1 and 2 disclose that plural flexible wiring substrates areconnected to one side of the display device.

In many cases, the flexible wiring substrates are used in a folded stateto make the display devices thin. In such a case, if the side of thedisplay device, to which the flexible wiring substrate is connected, isbent, the flexible wiring substrate receives a strong stress in afolding direction. Patent document 3 discloses to form a slit in theflexible substrate to mitigate the stress.

In a state in which the flexible wiring substrates are used in a foldedstate, there occurs a chance of short circuit between the wirings of theflexible wiring substrate and the wiring in another substrate when theflexible wiring substrate is being connected. Patent document 4, tocountermeasure this problem, discloses to form the connecting terminalsand the wirings separately on the different surfaces, namely, the frontsurface and the back surface of the flexible wiring substrate.

-   Patent document 1: Japanese patent application laid open No.    2009-168904-   Patent document 2: U.S. Pat. No. 9,560,761-   Patent document 3: Japanese patent application laid open No. Hei    3-65925-   Patent document 4: Japanese patent application laid open No.    2011-169983

SUMMARY OF THE INVENTION

When the flexible wiring substrate is connected along the curved side ofthe substrate, in addition, when the flexible substrate is bent orfolded, the stresses in complex directions are generated in the flexiblewiring substrate. At the same time, the portion of the display device,to which the flexible wiring substrate is connected, receives thestresses as a reaction.

When the glass substrate is used in the display device or in the sensordevice, the glass substrate must be thin so that it can be curved. Insuch a case, the glass substrate may be broken by the stresses when theflexible wiring substrate is bent. On the other hand, when the resinsubstrate is used, the curvature of the display device or sensorsubstrate is changed at the connecting portion with the flexible wiringsubstrate due to the stresses when the flexible wiring substrate isbent.

The stress may be mitigated by separating the flexible wiring substratein plural part; however, there are cases that the flexible wiringsubstrate must be separated in many parts according to the curvature ofthe side of the display panel. On the other hand, when a slit is formedin the flexible wiring substrate, in many cases, there is a chance thatenough stress mitigation is not attained according to the wiring layoutin the flexible wiring substrate.

The purpose of the present invention is to realize a structure to reducethe stress in the connecting portion of the curved side of the displaydevice or the sensor substrate to which the flexible wiring substrate isconnected even when the flexible wiring substrate is bent or folded; andconsequently, to realize the display devices and the sensor devices thatcan be adopted in various usages.

The present invention overcomes the above explained problem; theconcrete structures are as follows.

(1) An electronic device including a X shaped flexible wiring substratein a plan view.

(2) A display device including:

a display panel having a first side extending in a first direction,

a wiring substrate having a second side extending in the firstdirection,

a flexible wiring substrate connecting the display device with thewiring substrate in a second direction, which intersects with the firstdirection,

in which the flexible wiring substrate connects with the display panelat a first region and a second region, the first region and the secondregion are separated in the first direction,

the flexible wiring substrate connects with the wiring substrate at athird region and a fourth region, the third region and the fourth regionare separated in the first direction,

the flexible wiring substrate has a first wiring group, which extendsobliquely with the first direction or the second direction, and a secondwiring group, which extends obliquely with the first direction or thesecond direction,

the first wiring group connects the first region with either one of thethird region and the fourth region,

the second wiring group connects the second region with either anotherone of the third region and the fourth region,

the flexible wiring substrate has a width w1 in the first directionbetween an outer edge of the first region and an outer edge of thesecond region,

the flexible wiring substrate has a width w2 in the first directionbetween an outer edge of the third region and an outer edge of thefourth region,

the flexible wiring substrate has a portion of shortest width w3 in thefirst direction between the first region and the third region, andbetween the second region and the fourth region.

(3) A display device including:

a display panel having a first side extending in a first direction,

a wiring substrate having a second side extending in the firstdirection,

a first flexible wiring substrate connecting the display device with thewiring substrate in a second direction, which intersects with the firstdirection,

a second flexible wiring substrate connecting the display device withthe wiring substrate in the second direction,

in which the first flexible wiring substrate connects with the displaypanel at a first region, and connects with the wiring substrate at athird region, the first region and the third region are connected toeach other by a first wiring group,

the second flexible wiring substrate connects with the display panel ata second region, and connects with the wiring substrate at a fourthregion, the second region and the fourth region are connected to eachother by a second wiring group,

the first wiring group of the first wiring substrate has a first V shapeincluding a first vertex in the first direction between the first regionand the third region,

the second wiring group of the second wiring substrate has a second Vshape including a second vertex in a reverse direction to the firstdirection between the second region and the fourth region,

the first flexible wiring substrate and the second flexible wiringsubstrate overlap at an overlapping portion as that the first V shapeand the second V shape overlap,

in an assembled state of the first flexible wiring substrate and thesecond wiring substrate,

the first region and the second region are separated in a plan view,

the third region and the fourth region are separated in a plan view,

a width in the first direction between an outer edge of the first regionand an outer edge of the second region is w1,

a width in the first direction between an outer edge of the third regionand an outer edge of the fourth region is w2,

-   -   a narrowest width w3 in the first direction exists at the        overlapping portion.

(4) A display device including:

a display panel having a first side extending in a first direction,

a wiring substrate having a second side extending in the firstdirection,

a first flexible wiring substrate connecting the display device with thewiring substrate in a second direction, which intersects with the firstdirection,

a second flexible wiring substrate connecting the display device withthe wiring substrate in the second direction,

in which the first flexible wiring substrate connects with the displaypanel at a first region, and connects with the wiring substrate at afourth region, the first region and the fourth region are connected by afirst wiring group,

the second flexible wiring substrate connects with the display panel ata second region, and connects with the wiring substrate at a thirdregion, the second region and the third region are connected to eachother by a second wiring group,

the first wiring group of the first wiring substrate extends straightlyand diagonally between the first region and the fourth region,

the second wiring group of the second wiring substrate extendsstraightly and diagonally between the second region and the thirdregion,

the first flexible wiring substrate and the second flexible wiringsubstrate cross and overlap at an overlapping portion between the firstregion and the fourth region and between the second region and the thirdregion,

in an assembled state of the first flexible wiring substrate and thesecond wiring substrate,

the first region and the second region are separated in a plan view,

the third region and the fourth region are separated in a plan view,

a width in the first direction between an outer edge of the first regionand an outer edge of the second region is w1,

a width in the first direction between an outer edge of the third regionand an outer edge of the fourth region is w2,

a narrowest width w3 in the first direction exists at the overlappingportion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the display device as a comparativeexample;

FIG. 2 is perspective view of the display device as another comparativeexample;

FIG. 3 is a plan view of the display device according to the presentinvention;

FIG. 4 is a plan view that shows displacements of the flexible wiringsubstrate when the display panel is curved in the comparative example;

FIG. 5 is a plan view that shows displacements of the flexible wiringsubstrate when the display panel is curved in the other comparativeexample;

FIG. 6 is a plan view that shows displacements of the flexible wiringsubstrate when the display panel is curved in the present invention;

FIG. 7 is a plan view that shows stresses in the flexible wiringsubstrate when the display panel is curved in the comparative example;

FIG. 8 is a plan view that shows stresses in the flexible wiringsubstrate when the display panel is curved in the other comparativeexample;

FIG. 9 is a plan view that shows stresses in the flexible wiringsubstrate when the display panel is curved in the present invention;

FIG. 10 is a plan view of the flexible wiring substrate;

FIG. 11 is a cross sectional view of FIG. 10 along the line A-A′;

FIG. 12 is a cross sectional view of FIG. 10 along the line B-B′;

FIG. 13 is a plan view of a first example of the flexible wiringsubstrate according to the present invention;

FIG. 14 is a plan view of a second example of the flexible wiringsubstrate according to the present invention;

FIG. 15 is a cross sectional view of FIG. 14 along the line C-C′;

FIG. 16 is a plan view of a third example of the flexible wiringsubstrate according to the present invention;

FIG. 17 is a plan view of a fourth example of the flexible wiringsubstrate according to the present invention;

FIG. 18 is a plan view of a fifth example of the flexible wiringsubstrate according to the present invention;

FIG. 19 is a plan view of a sixth example of the flexible wiringsubstrate according to the present invention;

FIG. 20 is a cross sectional view of FIG. 19 along the line D-D′;

FIG. 21 is a plan view of a seventh example of the flexible wiringsubstrate according to the present invention;

FIG. 22 is a cross sectional view in which the flexible wiring substrateof FIG. 21 is bent;

FIG. 23 is a plan view of an example of the flexible wiring substrate inwhich the driver IC and the wirings are added in the structure of FIG.21 ;

FIG. 24 is a plan view of another example of the flexible wiringsubstrate in which the driver IC and the wirings are added in thestructure of FIG. 21 ;

FIG. 25 is a plan view of an eighth example of the flexible wiringsubstrate according to the present invention;

FIG. 26 is a cross sectional view in which the flexible wiring substrateof FIG. 25 is bent;

FIG. 27 is a plan view of an example of the flexible wiring substrate inwhich the driver IC and wirings are added in the structure of FIG. 25 ;

FIG. 28 is a plan view of a general structure of the flexible wiringsubstrate according to the present invention;

FIG. 29 is a plan view of a ninth example of the flexible wiringsubstrate according to the present invention;

FIG. 30 is a plan view of a tenth example of the flexible wiringsubstrate according to the present invention; and

FIG. 31 is a plan view of an eleventh example of the flexible wiringsubstrate according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail referring to thefollowing embodiments. The present invention will be used in variousdisplay devices having electro optic layers as the liquid crystaldisplay devices, the electrophoresis display devices and so forth, andfurther the self-luminescent display devices as the organic EL displaydevices, the micro LED display devices and so forth. The presentinvention will also be used in various sensor devices such as theexternal touch sensors or the figure print sensors and so forth.

Naturally, the present invention can also be used in other electronicdevices other than the display devices and the sensor devices.

The display device in the following embodiments can be substituted bythe sensor substrate of the sensor device or the substrate of theelectronic device to which the flexible wiring substrate is connected.

Embodiment 1

FIG. 1 is a perspective view of the display device as a comparativeexample. In FIG. 1 , the display panel 10 is curved like an arrow A inthe x axis direction by radius of curvature of R. The display panel 10may be the liquid crystal display panel, the organic EL display panel,or other thin display panels that can be curved. The flexible wiringsubstrate 20, which supplies the power or signals to the display panel10, is connected to the curved side of the display panel 10. The wiringsubstrate 30 connects to the other side of the flexible wiring substrate20. The wiring substrate 30 is, e.g. a PCB substrate, rigid and straightin the x axis direction as depicted by arrow B in FIG. 1 . The wiringsubstrate 30, however, can be curved in a direction along the curve ofthe display panel 10.

As a result, a twist stress is generated in the flexible wiringsubstrate 20 even in a state of FIG. 1 . In FIG. 1 , the flexible wiringsubstrate 20 is expected to be folded back in the direction of arrow Cto make the size of the display device compact and thin. When theflexible wiring substrate 20 is folded back, bending forces are appliedfrom two directions in the flexible wiring substrate 20; consequently,complex and large stresses are generated in the flexible substrate 20.Therefore, it is very difficult to bend the flexible wiring substrate 20in the direction shown by arrow C because of the stresses due to bendingor twisting caused by connecting the flexible wiring substrate 20 to thecurved side of the display panel 10; bending the flexible wiringsubstrate forcibly causes a breaking of the display panel 10 or severedeformation in the flexible wiring substrate 20. Even if the flexiblewiring substrate 20 could be bent, after it is connected to the curvedside of the display 10, there could be a chance of disconnection betweenthe flexible wiring substrate 20 and the display panel 10. Further, theflexible wiring substrate 20 will come off from the display panel 10.

The flexible wiring substrate 20 is formed as that the wirings made ofe.g. cupper are formed on the resin substrate made from e.g. polyimide.The polyimide, constituting substrate, is mechanically strong, thus,there is less danger that the polyimide substrate is broken. On theother hand, the same stress generated in the flexible wiring substrate20 is also applied to the display panel 10 as a reaction. When thesubstrate 10 is made of glass, a thickness is made as thin as 0.2 mm orless so that it can be curved; thus, there is a chance that the glasssubstrate 10 is broken. When the substrate 10 is made of resin, there isless chance that the substrate 10 is broken; however, the curvature ofthe display panel 10 is changed because of the reaction. Therefore, thestress formed in the flexible wiring substrate 20 in the followingexplanation can be paraphrased as the stress in the display panel 10.

In the meantime, the reaction of the stress generated in the flexiblewiring substrate 20 is also applied to the wiring substrate 30; however,the wiring substrate 30 is formed from mechanically strong resin, thus,a possibility that the substrate 30 is broken is very low. In addition,a change in curvature in the wiring substrate 30 does not raise aproblem. Therefore, in the explanation herein after, the reaction meansa reaction generated in the display panel 10.

FIG. 1 is a structure of the flexible wiring substrate 20 being dividedinto two rectangular flexible wiring substrates 20 to mitigate thestress in the flexible wiring substrate 20. The structure of FIG. 1 ,however, does not give enough stress relief. Specifically, where theflexible wiring substrates 20 are folded back in the direction of arrowC, the display panel may be broken if the glass substrate is thin. Inaddition, since the flexible wiring substrate 20 is also curved alongthe curve of the side of the display panel 10, it is difficult to foldback the flexible wiring substrate 20; if the flexible substrate 20 isforcibly folded back as shown by arrow C, the display panel 10 isdeformed severely.

FIG. 2 is a perspective view of comparative example whichcountermeasures the above explained problem. In FIG. 2 , the displaypanel 10 and the wiring substrate 30 are the same as explained in FIG. 1. The flexible wiring substrate 20 is divided into two; the plan view ofeach of the flexible wiring substrate 20 is an hourglass shape. In sucha flexible wiring substrate 20, the stress is mitigated when it is bentbecause the narrowed portion is easy to be bent. However, even thestructure of FIG. 2 does not give enough stress relief.

FIG. 3 is a perspective view of the display device according to thepresent invention. In FIG. 3 , the display panel 10 and the wiringsubstrate 30 are the same as explained in FIG. 1 . The plan view of theflexible wiring substrate of 20 is X shaped in FIG. 3 . Namely, in aplan view, the delta shaped cut out 201 is formed at the upper side andthe lower side (in y direction); the delta shaped cut out 202 is formedat the left side and the right side (in x direction).

A width of the flexible wiring substrate 20 in y direction becomesnarrower in going to the edge of the display panel in direction x alongthe connection portion. Since a width of the flexible wiring substrateis least at the largest displacement portion when the display panel 10is curved as shown by arrow A in FIG. 3 , the stress in the flexiblewiring substrate 20 is low. In addition, a width of the flexible wiringsubstrate 20 in y direction at the center in x direction is small due tothe cut out 201, the flexible wiring substrate is easier to be bent in xaxis direction; thus, the stress is further mitigated. At the same time,the reaction to the display device 10 is also reduced.

When the flexible wiring substrate 20 is bent or folded as shown byarrow C in FIG. 3 , a bending stress is mitigated because a width in xdirection of the flexible wiring substrate 20 at the center in ydirection is small due to the existence of the delta shaped cut out 202.

As a result, the stresses in the flexible wiring substrate 20 aremitigated in cases both when the flexible wiring is curved as shown byarrow A and when it is folded back as shown by arrow C in the structureof FIG. 3 . At the same time, the stress in the display panel 10 causedby the reaction from the stress of the flexible wiring substrate 20 ismitigated.

FIGS. 4 to 6 , which correspond to FIGS. 1 to 3 , are perspective viewsthat show displacements in the flexible wiring substrate 20 when thedisplay panel 10 is curved by a radius of curvature R while the wiringsubstrate 30 is kept flat. In FIGS. 4 to 6 , the width w3 and the radiusof curvature R of the flexible wiring substrate 20 are the same. Theradius of curvature R is selected as the camber is 1.6 mm when a chordof the arc w3 is 97.6 mm. In FIGS. 4 to 6, in x direction in theflexible wiring substrates 20, the width w1=36 mm, the gap or the cutout w2=25.6 mm, and the width w3=97.6 mm are common. The length h=24 mmin y direction of the flexible wiring substrates 10 is common in FIGS. 4to 6 .

In FIG. 4 , w1 is a width of each of the flexible wiring substrate 20;w2 is a space between the two flexible wiring substrates 20; w3 is awidth of outer edge to outer edge of two flexible wiring substrates 20.In FIG. 4 , numbers connoted to the contours in the flexible substrate20 correspond to displacements in z direction from the tangent plane tothe flexible wiring substrate 20.

As shown in FIG. 4 , the displacement, which is 1.6 mm, is largest atthe outer most edges of the two flexible wiring substrates 20 in theconnecting side with the display panel 10. The displacement graduallydecreases approaching to zero in going to the inner edge of the flexiblewiring substrate 20 at the connecting side with the display panel 10.

FIG. 5 shows displacements of the flexible wiring substrate 20 when aplan view of the flexible wiring substrate 20 is like the hour glass. InFIG. 5 , notations of R, w1, w2, and w3 are the same as FIG. 4 . Themeaning of the contours is the same as explained in FIG. 4 . In FIG. 5 ,a narrow portion exists, which is a feature of the hour glass, theamount of cut out w11 at the narrow portion is 6 mm.

The displacements of the flexible wiring substrate 20 in FIG. 5 arealmost the same as the displacements in FIG. 4 . Namely, thedisplacement, which is 1.6 mm, is largest at the outer most edges of thetwo flexible wiring substrates 20 at the connecting side with thedisplay panel 10. The displacement gradually decreases approaching tozero in going to the inner edge of the flexible wiring substrate 20 inthe connecting side with the display panel 10.

FIG. 6 shows displacements of the flexible wiring substrate 20 accordingto the present invention. In FIG. 6 , the radius of curvature R is thesame as in FIGS. 4 and 5 . In FIG. 6 , the flexible wiring substrate 20is divided into two portions by delta shaped cut out 201 at theconnecting side with the display panel 10; a width in x direction ofeach of the portions is w1, and a width in x direction of the cut out isw2; a width in x direction from outer edge to outer edge, namely, atotal width of the flexible wiring substrate 20 is w1. The meaning ofthe contours in FIG. 6 is the same as explained in FIG. 4 .

The displacements of the flexible wiring substrate 20 in FIG. 6 are verydifferent from the displacements of the flexible wiring substrate 20 inFIGS. 4 and 5 . The displacement, which is 1.6 mm, is largest at theouter most edges of the flexible wiring substrate 20 at the connectingside with the display panel 10. The displacement at the upper horn ofthe flexible wiring substrate 20 gradually decreases in going to theroot of the horn; the displacement is almost zero at the center of theflexible wiring substrate 20.

Namely, in the flexible wiring substrate 20 according to the presentinvention, the bending stress is almost zero at the vicinity of thecenter of the flexible wiring substrate 20. Therefore, only a simplestress is generated when the flexible wiring substrate 20 with thewiring substrate 30 of FIG. 6 is bent back to the rear, which is thesame as when a flat flexible wiring substrate is bent back to the rear.

FIGS. 7 to 9 , which correspond to FIGS. 4 to 6 , show the stressdistribution in the flexible wiring substrate 20. FIGS. 7 to 9 areexpressed so called von Mises stress, which takes into account all thestresses in x direction, y direction and z direction, can evaluate thevalue of the stress regardless the directions of the stress.

FIG. 7 is a stress distribution when the flexible wiring substrate 20 ofthe first comparative example is bent as shown FIG. 4 . The numberscorresponding to the contours in FIG. 7 are values of stress, the unitis MPa. The stress is large, as 24, at the outer edge of the flexiblewiring substrate 20 in the connecting side with the display panel 10.The stress gradually becomes smaller in going to the inner edge of theflexible wiring substrate 20 in the connecting side with the displaypanel 10. The largest stress in FIG. 7 is 41.8. The same stress isgenerated at the corresponding edge of the display panel 10 as areaction.

FIG. 8 is a stress distribution when the flexible wiring substrate 20 ofthe second comparative example is bent as shown FIG. 5 . The numberscorresponding to the contours in FIG. 8 are the same as explained inFIG. 7 . The largest stress in FIG. 8 is 48.1, which occurs at thenarrow portion of the hour glass shape. Therefore, the stress can bemitigated by changing the shape of the narrow portion.

In FIG. 8 , the largest stress in the side where the flexible wiringsubstrate 20 connects with the display panel 10 is 9, which is reducedcompared with the structure of FIG. 7 . Therefore, the stress generatedin the display panel 10 as a reaction is also decreased.

FIG. 9 is a stress distribution when the flexible wiring substrate 20according to the present invention is bent as shown FIG. 6 . The numberscorresponding to the contours in FIG. 9 are values of stress, the unitis MPa. The stress in FIG. 9 is almost zero, which is very differentfrom the stresses in FIGS. 7 and 8 . Namely, no region exists where thestress is larger than 3 MPa in FIG. 9 .

In FIG. 9 , the stress is large as 5.8 MPa at the tip of the cut out202; however, it is an abnormal point due to acute and sharp angle ofthe cut out 202, therefore, if the acute and sharp angle of the cut out202 is substituted by a smooth curve, the stress can be substantiallyreduced. Anyway, the maximum stress is generated in the flexible wiringsubstrate 20 itself, thus, this stress does not generate the stress inthe display panel 10 as a reaction.

As shown in FIG. 9 , the stress is actually not generated in theflexible wiring substrate 20 according to the present invention when thedisplay panel 10 is curved, therefore, a complex stress is not generatedeven when the flexible wiring substrate 20 is bent back; therefore, itcan be considered as that a flat flexible wiring substrate 20 is bentback. The reason why the stress is reduced in the flexible wiringsubstrate 20 according to the present invention is the same as thatexplained in FIG. 3 . In other words, the delta shaped cut outs 201 and202 have a large influence.

FIG. 10 is a plan view of a general flexible wiring substrate 20. InFIG. 10 , wirings 21, formed from e.g. cupper, is patterned on thesubstrate 22 formed from resin as e.g. polyimide. The protecting film 23is formed to cover the cupper wirings 21. The protecting film 23 can beso called a solder resist. The protecting film 23 covers the cupperwirings 21 except terminal portions in which the cupper wirings connectwith the display panel 10 or the wiring substrate 30.

FIG. 11 is a cross sectional view of FIG. 10 along the line A-A′. FIG.12 is a cross sectional view of FIG. 10 along the line B-B′. In FIGS. 11and 12 , the cupper wirings 21 are formed in predetermined pitch; theprotecting film 23 is formed to cover the cupper wirings 21.

FIG. 13 is an example of the flexible wiring substrate 20 according tothe present invention. In FIG. 13 , X shaped flexible wiring substrate20 connects the display panel 10 with the wiring substrate 30. Since thewirings 21 in the flexible wiring substrate 20 of FIG. 13 is a singlelayer, the wirings 21 are V shaped. Namely, the wirings 21, connected atthe region (1) with the display panel 10, bend at the center of theflexible wiring substrate 20 in V shape and connect with the wiringsubstrate 30 at the region (3). The wirings 21, connected at the region(2) with the display panel 10, bend at the center of the flexible wiringsubstrate 20 in V shape and connect with the wiring substrate 30 at theregion (4).

The terminal region (1) can be paraphrased as a first terminal group ofthe flexible wiring substrate 20; the terminal region (2) can beparaphrased as a second terminal group of the flexible wiring substrate20; the terminal region (3) can be paraphrased as a third terminal groupof the flexible wiring substrate 20; the terminal region (4) can beparaphrased as a fourth terminal group of the flexible wiring substrate20. Each of the first terminal group to the fourth terminal group is aterminal group consisting of plural terminals arranged in x direction.Terminal groups are also formed in the display panel 10 corresponding tothe terminal groups of the flexible wiring substrate 20.

FIG. 14 is a plan view of the X shaped flexible wiring substrate 20,which is formed from two of the V shaped flexible wiring substrates 20.In FIG. 14 , V shaped wirings 21 are formed in each of the two V shapedflexible wiring substrates 20. The two V shaped wiring substrates 20overlap at the V shaped bending portions; as a result, the plan viewbecomes X shape.

FIG. 15 is a cross sectional view of FIG. 14 along the line C-C′. Theclock signals or video signals of high frequency are supplied to thewiring of each of the two flexible wiring substrate 20, therefore, aninterference must be avoided. In FIG. 15 , the conductive films 24 areformed on the opposing surfaces of the flexible wiring substrate 20 toavoid the interference. There is a space between the two wiringsubstrates 20 in FIG. 15 ; however, the space is just for depiction oftwo separate flexible wiring substrates 20; generally, the space is notnecessary.

FIG. 16 is an alternative example of FIGS. 14 and 15 . FIG. 16 is a planview in which the structure of FIG. 13 is formed from two deformed Vshaped flexible wiring substrates 20. FIG. 16 differs from FIGS. 14 and15 in that: the two V shaped flexible wiring substrate 20 do not overlapin a plan view; and the opposing portions of the two V shaped flexiblewring substrates 20, at which the wirings bend, are truncated to bestraight. Namely, each of the two flexible wiring substrates 20 has a Vshaped cut out at one side and a straight portion at another side in thehorizontal direction; the two flexible wiring substrates 20 are set sideby side to form a X shaped flexible wiring substrate 20 as a total.Liberty in wring layout can be improved by forming a straight portion inthe flexible wiring substrate 20.

FIG. 17 is a second alternative example of FIGS. 14 and 15 . The stresstends to be high at the tip of the V shape in the V shaped flexiblewiring substrate 20. Especially, when the wiring 21 is turned in Vshape, and the flexible wiring substrates 20 is bent at this portion, abreaking of the wiring 21 tends to occur. In FIG. 17 , the tip of the Vshape is substituted by the arc to mitigate the stress. As a result, abreaking of the flexible wiring substrate 20 and disconnection of thewirings 21 can be avoided. The flexible wiring substrate 20 of FIG. 17still maintain X shape in a plan view.

In FIG. 18 , the two flexible wiring substrates 20 of parallelogram areoverlapped to form a X shaped flexible substrate 20 in a plan view.Since there is no bending portion in the wirings in each of the flexiblewiring substrates 20, a risk of disconnection of the wirings 21 is verylow. In FIG. 18 , the terminal region (1) of the display device 10 andthe terminal region (4) of the terminal substrate 30 are connected toeach other by one flexible wiring substrate 20 and the terminal region(2) of the display device 10 and the terminal region (3) of the wiringsubstrate 30 are connected to each other by another flexible wiringsubstrate 20. The cross sectional view of the overlapped portion of thetwo wiring substrate 20 in FIG. 18 is the same as FIG. 15 .

FIG. 19 is an example in which the structure of the flexible wiringsubstrate 20 of FIG. 18 is formed by one X shaped flexible wiringsubstrate 20. In FIG. 19 , the outer shape of the flexible wiringsubstrate 20 is X shape. The wirings 212 formed in the flexible wiringsubstrate 20 are formed on the rear surface of the substrate 22 asdepicted by broken lines in FIG. 19 . In the place where the wirings 212intersect, one group of the wirings 212 connects with wirings 211 on thefront surface via the through holes 25; then, after the intersect, theone group of the wirings 211 on the front surface connects with thewirings 212 on the rear surface via the through holes 25.

FIG. 20 is a cross sectional view of FIG. 19 along the line D-D′. InFIG. 20 , the back wirings 212 are formed on the back surface of thesubstrate 22. The back wirings 212 connect with the front wirings 211via the through holes 25 at the place of intersection; the front wirings211 connect with the back wirings 212 via the through holes 25 after theintersection. Both the front wirings and the back wirings are covered byprotecting film 23.

FIG. 21 is an alternative example of the X shape flexible wiringsubstrate 20. The feature of FIG. 21 is that the intersection in X shapeis nearer to the display device 10 than to the wiring substrate 30; inother words, y1<y2 and x1<x2. When the display device is curved as arrowA in FIG. 21 while the wiring substrate 30 is kept flat, a stress isgenerated in the flexible wiring substrate 20; the stress in the side ofthe display device 10 is smaller when x1 is smaller. Therefore, thestructure of FIG. 21 has a merit to mitigate the stress in the displaypanel 10.

When the flexible wiring substrate 20 is folded back to the rear of thedisplay panel 10, the flexible wiring substrate 20 is bent at the crossportion, namely, at the distance y1 from the top of the flexible wiringsubstrate 20. Since y1 is smaller than y2, the flexible wiring substrate20 is bent in a radius of curvature smaller than (y1+y2)/2, which is ahalf of the length in y direction of the flexible wiring substrate 20.

FIG. 22 is a cross sectional view when the flexible wiring substrate 20is bent to the back of the display panel 10. The flexible wiringsubstrate 20 of the structure of FIG. 21 can be bent in a small radius,therefore, d1 in FIG. 22 can be made smaller. Thus, the outer size ofthe display device can be made smaller, especially, the frame width canbe made narrower at the side where the flexible wiring substrate 20 isbent.

FIG. 23 is an example in which the driver IC 15 is installed on thedisplay panel 10. Since an upper width x1 of the flexible wiringsubstrate 20 is small, one driver IC 15 covers the wirings in FIG. 23 .FIG. 24 is an example in which the two IC drivers 15 are provided in thedisplay device 10 corresponding to the terminal regions of the flexiblewiring substrate 20. Since the wirings 11 are dense specifically at twovertical sides of the display panel 10, extremely fine pitches inwirings, especially in the diagonal wirings, can be avoided by settingtwo driver ICs 15 as shown in FIG. 24 .

FIG. 25 is another alternative example of the X shape flexible wiringsubstrate 20. The feature of FIG. 25 is that the intersection in X shapeis nearer to the wiring substrate 30 than to the display device 10; inother words, y1>y2 and x1>x2. When the display device is curved as arrowA in FIG. 21 while the wiring substrate 30 is kept flat, a stress isgenerated in the flexible wiring substrate 20; the stress in the side ofthe display device 10 is larger when x1 is larger. Therefore, thestructure of FIG. 25 is not necessarily so suitable when the displaypanel 10 is curved by a small radius of curvature.

When the flexible wiring substrate 20 is folded back to the rear of thedisplay panel 10, the flexible wiring substrate 20 is bent at the crossportion, namely, at the distance y1 from the top of the flexible wiringsubstrate 20. Since y1 is larger than y2, the flexible wiring substrate20 is bent in a radius of curvature larger than (y1+y2)/2, which is ahalf of the length in y direction of the flexible wiring substrate 20.

FIG. 26 is a cross sectional view when the flexible wiring substrate 20of FIG. 25 is bent to the back of the display panel 10. The flexiblewiring substrate 20 of the structure of FIG. 25 is to be bent in rathera larger radius; in other words, d2 in FIG. 26 is larger than d1 in FIG.22 . Therefore, the structure of 25 is not so suitable when the outersize of the display device is desired to be small.

FIG. 27 is an example in which the driver ICs 15 are installed on thedisplay panel 10 in the structure of FIG. 25 . In FIG. 27 , the driverICs 15 can be set further outer sides than the structure of FIG. 24 .Even the wirings 11 are dense specifically at two vertical sides of thedisplay panel 10, extremely fine pitches in wirings can be avoided bysetting the driver ICs 15 at further outer sides as shown in FIG. 27 .In other words, the angle of wiring η2 in FIG. 27 can be made smallerthan the angle of wiring η1 in FIG. 24 . Consequently, the pitches inthe diagonal wirings 11 in the structure of FIG. 27 can be made lager,thus, design margin for layout of wirings can be increased.

In the above explanations, the driver ICs 15 are set on the displaypanel 10 by so called COG (Chip On Glass). However, the relation betweenthe driver IC 15 and the flexible wiring substrate 20 are not limited inthat structure; the driver IC 15 can be installed on the X shapedflexible wiring substrate 20 according to the present invention; thisstructure is referred to as COF (Chip On Film).

FIG. 28 is a perspective view of a general shape of the flexible wiringsubstrate 20 according to the present invention. A general shape of theflexible wiring substrate 20 according to the present invention is Xshaped, however, this X shape is not necessarily constituted fromcrossed parallelograms

In FIG. 28 , θ1 and θ2 are not necessarily the same value. Each of θ1and θ2 can take a value between 10 degrees to 80 degrees. In FIG. 28 ,if θ1+θ2<θ3, it is emphasized that the flexible wiring substrate 20 islonger in horizontal direction. The value of θ1+θ2 can be set between 20degrees and 90 degrees. The values of θ3 are preferably set as 180degrees minus 2×θ1; the value of 04 is preferably set as 180 degreesminus 2×θ2. Each of the values of θ3 and θ4 are set larger than 90degrees and smaller than 180 degrees.

When the display panel 10 is curved as shown in FIGS. 1 to 3 , and theflexible wiring substrate 20 is bent back to the rear of the displaypanel 10, in the structure of FIG. 28 , the stress in the flexiblewiring substrate 20 and the stress as a reaction in the display panel 10can be reduced by making the length A longer, and making the length Bshorter.

FIG. 29 is a plan view of another example of X shaped flexible wiringsubstrate 20 according to the present invention. The feature of theflexible wiring substrate 20 of FIG. 29 is that V shaped tips in the cutouts 201 and 202 are substituted by smooth curves as a radius ofcurvature R1 and a radius of curvature R2. Thus, local large stress inthe flexible wiring substrate 20 can be avoided; consequently,disconnections in the wirings 21 in the flexible wiring substrate 20 canbe avoided.

FIG. 30 is a plan view of yet another example of X shaped flexiblewiring substrate 20 according to the present invention. The feature ofthe flexible wiring substrate 20 of FIG. 30 is that notches 26 areformed at the portions where large stress is generated to avoid a locallarge stress in the flexible wiring substrate 20. Another feature of thestructure of FIG. 30 is that a slit 27 is formed at the center of theflexible wiring substrate 20. The slit 27 mitigates the stress when theflexible wiring substrate 20 is bent back to the rear of the displaypanel 10; as a result, the stress as a reaction in the display panel 10is also mitigated.

FIG. 31 is a plan view of yet another example of X shaped flexiblewiring substrate 20 according to the present invention. The feature ofthe flexible wiring substrate 20 of FIG. 31 is that central projections28 are formed; the central projections 28 extend in y direction or −ydirection at the center in x direction of the flexible wiring substrate20. The cut out 201 is divided into cut out 203 and cut out 204 by thecentral projection 28.

The wirings 21 are formed also in the central projections 28, and thewirings 21 are connected to the display panel 10 and to the circuitsubstrate 30. Therefore, the flexible wiring substrate 20 of FIG. 31connects to the display panel 10 and to the wring substrate 30 at threeregions; thus, design liberty in wiring can be increased as well as thebending stress can be mitigated. In the structure of FIG. 31 , easinessof bending of the flexible wiring substrate 20 and generation of stressin the flexible wiring substrate 20 are adjusted by the length A and thelength B as other example of X shaped flexible wiring substrate 20.

What is claimed is:
 1. A display device comprising: a display panelhaving a first side extending in a first direction, a wiring substratehaving a second side extending in the first direction, and a flexiblewiring substrate connecting the display device with the wiring substratein a second direction, which intersects with the first direction,wherein the flexible wiring substrate connects with the display panel ata first region and a second region, the first region and the secondregion are separated in the first direction, the flexible wiringsubstrate connects with the wiring substrate at a third region and afourth region, the third region and the fourth region are separated inthe first direction, the flexible wiring substrate has a first wiringgroup, which extends obliquely with the first direction or the seconddirection, and a second wiring group, which extends obliquely with thefirst direction or the second direction, the first wiring group connectsthe first region with either one of the third region and the fourthregion, the second wiring group connects the second region with eitheranother one of the third region and the fourth region, the flexiblewiring substrate has a width w1 in the first direction between an outeredge of the first region and an outer edge of the second region, theflexible wiring substrate has a width w2 in the first direction betweenan outer edge of the third region and an outer edge of the fourthregion, and the flexible wiring substrate has a portion of shortestwidth w3 in the first direction between the first region and the thirdregion, and between the second region and the fourth region.
 2. Thedisplay device according to claim 1, wherein the first width w1 and thesecond width w2 are equal.
 3. The display device according to claim 1,wherein the portion of shortest width w3 in the first direction islocated at a center in the second direction between the first region andthe third region or between the second region and the fourth region. 4.The display device according to claim 1, wherein the first width w1 isshorter than the second width w2.
 5. The display device according toclaim 1, wherein the portion of shortest width w3 in the first directionis located nearer to the display panel than the wiring substrate.
 6. Thedisplay device according to claim 1, wherein the first wiring groupconnects the first region with the third region, the second wiring groupconnects the second region with the fourth region, the first wiringgroup bends at the portion of width w3 in V shape in a plan view, andthe second wiring group bends at the portion of width w3 in V shape in aplan view in a opposite bending direction to the bending direction ofthe first wiring group.
 7. The display device according to claim 1,wherein the first wiring group connects the first region with the fourthregion, the second wiring group connects the second region with thethird region, and an insulating film is formed between the first wiringgroup and the second wiring group at a position in which the firstwiring group and the second wiring group cross.
 8. The display deviceaccording to claim 7, wherein the insulating film is a base substrate ofthe flexible wiring substrate.
 9. The display device according to claim1, wherein the flexible wiring substrate connects with the displaydevice at a fifth region, which is between the first region and thesecond region, the fifth region and the first region are separated andthe fifth region and the second region are separated, and the flexiblewiring substrate connects with the wiring substrate at a sixth region,which is between the third region and the fourth region, the sixthregion and the third region are separated and the sixth region and thefourth region are separated, the flexible wiring substrate has extendingportions in the second direction between the fifth region and the sixthregion.
 10. The display device according to claim 1, wherein the displaydevice curves along the first direction.
 11. The display deviceaccording to claim 10, wherein the wiring substrate is turned back to aback of the display panel via the flexible wiring substrate.
 12. Adisplay device comprising: a display panel having a first side extendingin a first direction, a wiring substrate having a second side extendingin the first direction, a first flexible wiring substrate connecting thedisplay device with the wiring substrate in a second direction, whichintersects with the first direction, and a second flexible wiringsubstrate connecting the display device with the wiring substrate in thesecond direction, wherein the first flexible wiring substrate connectswith the display panel at a first region, and connects with the wiringsubstrate at a third region, the first region and the third region areconnected to each other by a first wiring group, the second flexiblewiring substrate connects with the display panel at a second region, andconnects with the wiring substrate at a fourth region, the second regionand the fourth region are connected to each other by a second wiringgroup, the first wiring group of the first wiring substrate has a firstV shape including a first vertex in the first direction between thefirst region and the third region, the second wiring group of the secondwiring substrate has a second V shape including a second vertex in areverse direction to the first direction between the second region andthe fourth region, the first flexible wiring substrate and the secondflexible wiring substrate overlap at an overlapping portion as that thefirst V shape and the second V shape overlap, in an assembled state ofthe first flexible wiring substrate and the second wiring substrate, thefirst region and the second region are separated in a plan view, thethird region and the fourth region are separated in a plan view, a widthin the first direction between an outer edge of the first region and anouter edge of the second region is w1, a width in the first directionbetween an outer edge of the third region and an outer edge of thefourth region is w2, and a narrowest width w3 in the first directionexists at the overlapping portion.
 13. The display device according toclaim 12, wherein a conductive film is formed between the first wiringgroup and the second wiring group.
 14. A display device comprising: adisplay panel having a first side extending in a first direction, awiring substrate having a second side extending in the first direction,a first flexible wiring substrate connecting the display device with thewiring substrate in a second direction, which intersects with the firstdirection, and a second flexible wiring substrate connecting the displaydevice with the wiring substrate in the second direction, wherein thefirst flexible wiring substrate connects with the display panel at afirst region, and connects with the wiring substrate at a fourth region,the first region and the fourth region are connected to each other by afirst wiring group, the second flexible wiring substrate connects withthe display panel at a second region, and connects with the wiringsubstrate at a third region, the second region and the third region areconnected to each other by a second wiring group, the first wiring groupof the first wiring substrate extends straightly and diagonally betweenthe first region and the fourth region, the second wiring group of thesecond wiring substrate extends straightly and diagonally between thesecond region and the third region, the first flexible wiring substrateand the second flexible wiring substrate cross and overlap at anoverlapping portion between the first region and the fourth region andbetween the second region and the third region, in an assembled state ofthe first flexible wiring substrate and the second wiring substrate, thefirst region and the second region are separated in a plan view, thethird region and the fourth region are separated in a plan view, a widthin the first direction between an outer edge of the first region and anouter edge of the second region is w1, a width in the first directionbetween an outer edge of the third region and an outer edge of thefourth region is w2, and a narrowest width w3 in the first directionexists at the overlapping portion.
 15. The display device according toclaim 14, wherein a conductive film is formed between the first wiringgroup and the second wiring group.